Neuro Exam 1

Neurons

The main functional units of the brain, capable of generating electrical signals known as nerve impulses.

Glia

Support cells of the nervous system that serve several important support roles for neurons.

Soma (Cell Body)

The main part of the neuron, housing the nucleus and much of the cellular organelles.

Dendrites

Extensions of the soma that receive incoming information.

Axon

A long extension that carries information away from the soma towards axon terminals.

Terminal Boutons

Structures in the axon terminals housing neurotransmitters, used to signal other cells.

Axon Hillock (Initial Segment)

The region where the axon attaches to the soma, where electrical currents can generate an action potential.

Action Potential (Nerve Impulse)

An electrical event generated at the initial segment that travels down the axon to the axon terminals, resulting in neurotransmitter release.

Unipolar Neurons

Neurons with a single process, found in the autonomic nervous system.

Bipolar Neurons

Neurons with two distinct processes (a dendritic structure and an axon), such as sensory neurons.

Multipolar Neurons

Neurons that typically have a single axon and branching dendritic structures; the most common type in vertebrates.

Brain Extracellular Fluid (BECF)

The watery extracellular (interstitial) environment of the brain.

Blood-Brain Barrier (BBB)

Separates the BECF from the intravascular system or space.

Neuropil

The area outside of neuronal cell bodies, composed of axonal and dendritic branches, and the synapses between them.

Brain Parenchyma

The functional tissue of the brain (neurons and glia), distinguished from structural or supporting elements.

Nucleus

A double-membraned organelle, typically centrally located, containing DNA (and some RNA), with nuclear pores; the site of transcription.

Cytoplasm

The location of most organelles, containing the cytosol (aqueous part of cytoplasm) and some freely soluble proteins; the site of translation.

Endoplasmic Reticulum (ER)

Often attached to the nuclear membrane; rough ER (rER) is embedded with ribosomes, smooth ER (sER) is not; involved with protein processing including posttranslational modifications.

Ribosomes

The site of protein synthesis.

Golgi Apparatus

The site of posttranslational modifications, protein sorting, and protein packaging.

Mitochondrion

The site of cellular respiration, the Krebs cycle, electron transport chain, and ATP production.

Plasmalemma (Cell Membrane)

The neuronal boundary, largely composed of phospholipids, providing a hydrophobic barrier impermeable to most water-soluble substances.

Phospholipids

Components of the neuronal membrane with both a polar (charged) and a nonpolar (uncharged) end, forming a hydrophobic inner membrane.

Integral Membrane Proteins

Proteins that serve as ligand-binding receptors, adhesion molecules, channels, carriers, pumps (for transmembrane movement of water-soluble substances), enzymes, and in intracellular signaling.

Peripheral Membrane Proteins

Proteins that can participate in intracellular signaling and form a submembranous cytoskeleton.

Microtubules

Cytoskeletal components (20-25 nm) composed of α- and β-tubulin protein subunits, serving in forming neuron shape and in transport, especially along axons.

Neurofilaments (Intermediate Filaments)

Cytoskeletal components (10 nm) that are the most abundant fibrillar component in axons, mostly stable and polymerized.

Microfilaments (Thin Filaments)

Cytoskeletal components (3-8 nm) composed of actin, concentrated near the cytoplasmic plasmalemma, undergoing cycles of polymerization and depolymerization.

Microglia

Immune cells of the nervous system, involved in antigen presentation and phagocytic cleanup.

Astrocytes

Macroglia that help regulate the neuroenvironment and support neuron functioning, including insulating neuronal groups, regulating K+ concentration, taking up neurotransmitters, releasing growth factors, and helping form the blood-brain barrier.

Oligodendrocytes

Glial cells associated with myelination within the CNS; one oligodendrocyte can envelop several axonal segments.

Schwann Cells

Glial cells associated with myelination within the PNS; one Schwann cell envelopes a single segment between two nodes of Ranvier.

Action Potential Characteristics

Not dependent upon stimulus intensity, "all-or-none events" with a fixed amplitude; increasing stimulus only increases their frequency.

Divergence

When one neuron sends output to numerous cells; common within the input stages of the nervous system.

Convergence

When one neuron receives input from numerous cells; common within the output stages of the nervous system.

Receptive Component

The dendrites, serving as the input region of a model neuron.

Summing (Integrative) Component

The cell body, serving as the integrative region of a model neuron.

Long-Range Signaling Component

The axon, serving as the conductive region of a model neuron.

Secretory Component

The axonal terminals, serving as the output (chemical) region of a model neuron.

Receptor Potentials

Graded potentials typical of sensory neurons, dependent on stimulus intensity, and spreading passively over short distances.

Gene Expression

The turning on of genes for making the various components of each cell and the brain as a whole.

Heritability

Defines the extent to which genetic factors account or contribute to observed traits in a population.

Identical (Monozygotic) Twins

Develop from a single fertilized egg and share the exact same genes.

Fraternal (Dizygotic) Twins

Develop from two different fertilized eggs and share about 50% of their genes, similar to normal siblings.

Concordance (in twin studies)

Increased likelihood of a given psychiatric or neurological trait in one identical twin if the other has it, compared to fraternal twins, supporting a hereditary component.

Gene

A sequence of DNA that codes for a particular protein or trait.

Nucleotide

The building block of DNA, containing a nitrogenous base (A, G, C, T/U), a 5-carbon sugar (deoxyribose/ribose), and a phosphate group.

DNA Base Pairing

Adenine (A) always pairs with Thymine (T), and Guanine (G) always pairs with Cytosine (C).

RNA Differences from DNA

Usually single-stranded, uses ribose instead of deoxyribose, and replaces Thymine (T) with Uracil (U).

Introns

Noncoding regions of DNA that are removed from exons before translation.

Exons

Coding regions of DNA.

Human Chromosomes

Humans have 46 homologous chromosomes (22 pairs of autosomes and one pair of sex chromosomes).

Meiosis I - Prophase I

Distinguished from mitosis by the pairing of duplicated homologous chromosomes and occurrence of crossing over.

Genotype

Refers to the genetic makeup of an individual.

Phenotype

Refers to the appearance or what is expressed.

Alleles

The two copies of a particular gene.

Recessive Trait

A phenotypic trait expressed only when both alleles are mutated (homozygous for the mutant allele).

Dominant Trait

A phenotypic trait resulting from a combination of one mutant allele and one wild-type allele.

Parental Imprinting

A type of gene regulation where only one of the two gene copies (either maternal or paternal) is expressed.

Angelman Syndrome

Inherited through the maternal line, resulting from a deletion of multiple genes on chromosome 15q11-q13, associated with mental retardation, epilepsy, and absence of speech.

Prader-Willi Syndrome

Inherited through the paternal line, resulting from a deletion of multiple genes on chromosome 15q11-q13, associated with obesity, obsessive-compulsive disorder, and bipolar disorder.

Phenylketonuria (PKU)

A neurological disease caused by two abnormal copies of the gene for phenylalanine hydroxylase, leading to accumulation of phenylalanine and toxic metabolites, resulting in mental retardation.

Peptide Bond

A CO-NH linkage formed when amino acids are joined through the elimination of a water molecule.

Polypeptides

Proteins with numerous amino acids joined by peptide bonds.

Primary Protein Structure

The amino acid sequence of a protein.

Secondary Protein Structure

Involves alpha helices and beta-pleated sheets.

Transcription

The synthesis of all RNA from the genetic code in DNA.

Translation

The synthesis of proteins from amino acids.

Codons

Triplets of bases in mRNA that determine which amino acid will be joined to the growing polypeptide chain.

Start Codon

AUG, which can code for methionine or function as a "start" signal for translation.

Stop Codons

UAA, UAG, UGA, which function to terminate translation.

Posttranslational Modification

Modification of proteins after their synthesis, such as disulfide linkage, acylation, isoprenylation, ubiquitination, and glycosylation.

Signal Peptides

A continuous stretch of amino acids, typically 15 to 60 residues long, that directs proteins to specific cellular compartments.

Signal Patches

A specific three-dimensional arrangement of atoms on a protein's surface that forms when the protein folds up, directing proteins to specific cellular compartments.

Gated Transport

Protein movement between compartments with continuity of their spaces, such as between the nucleus and the cytosol, where nuclear pores act as a gate.

Trans-membrane Transport

Protein movement between two distinct compartments, often requiring proteins to unfold to pass through a membrane-bound protein translocator.

Vesicular Transport

Protein movement using transport vesicles to ferry proteins from one compartment to another, e.g., from the ER to the Golgi.

Microtubules (in transport)

Provide the "track" on which specific organelles, vesicles, and macromolecules are moved by molecular motors over long distances in neurons.

Kinesin

A motor protein (ATPase) that aids fast anterograde movement along microtubules (towards the plus end, away from the cell body).

Dynein

A motor protein (ATPase) that aids fast retrograde movement along microtubules (towards the minus end, towards the cell body).

Exocytosis

The process by which secretory vesicles fuse with the cell membrane to release their contents (e.g., neurotransmitters) into the extracellular space.

Endocytosis

The process by which plasmalemmal membrane is taken up into the cell in the form of endocytic vesicles (e.g., to recycle synaptic vesicles).